Dr. Raoul Trines

Central Laser Facility, Rutherford Appleton Laboratory

About:

Raoul Trines is a Senior Research Scientist at the Central Laser Facility (Rutherford Appleton Laboratory) and a Visiting Researcher at Oxford University’s Physics Department. He previously worked at Eindhoven University of Technology’s Department of Applied Physics and the Space Science and Technology Department at the Rutherford Appleton Laboratory.

Raoul holds a masters degree in both mathematics and applied physics from Eindhoven University of Technology. His Ph.D. research (1998-2003), also at Eindhoven University, focused on laser acceleration of electrons in plasma. After working as a post-doctoral fellow at the Space Science and Technology Department at RAL (2003-2005), he has worked as a researcher at the Central Laser facility since 2005, doing theoretical and numerical research into laser-plasma interactions.

His current research programme focuses on the nonlinear interaction of lasers with low-density plasma, especially laser-plasma instabilities such a s Raman and Brillouin amplification. More recently, he has also explored the use of higher-order laser modes (Laguerre-Gaussian or Hermite-Gaussian) in laser-plasma instabilities and also in laser-plasma high harmonic generation.

Abstract:
Laser harmonic generation: a beat wave on steroids

In previous studies of spin-to-orbital angular momentum (AM) conversion in laser high harmonic generation (HHG) using a plasma target, one unit of spin AM is always converted into precisely one unit of OAM [1, 2]. Here we show, through analytic theory and numerical simulations, that we can exchange one unit of SAM for a tuneable amount of OAM per harmonic step, via the use of a structured plasma target. In the process, we introduce a novel framework to study laser harmonic generation via recasting it as a beat wave process. This framework enables us to easily calculate and visualise harmonic progressions, unify the “photon counting” and “symmetry-based” approaches to HHG, and to provide new explanations for existing HHG results. Our framework also includes a specific way to analyse simultaneously the frequency, spin and OAM content of the harmonic radiation which provides enhanced insight into this process. We will present the results of simulations of laser pulses interacting with targets having either a structured reflective surface or a structured aperture, and apply our framework to analyse the harmonic spectra from the laser-target interactions [3]. The prospects of using our new frame-work to design HHG configurations with tuneable high-order transverse modes, also covering the design of structured plasma targets, will be discussed.

References:
[1] J. W. Wang, M. Zepf and S. G. Rykovanov, Nature Communications 10, 5554 (2019).
[2] Shasha Li et al., New J. Phys. 22, 013054 (2020).
[3] R. Trines et al., “Laser harmonic generation with independent control of frequency andorbital angular momentum”, submitted (2023),https://doi.org/10.21203/rs.3.rs-3458883/v1